The present invention relates to tires with radial carcass reinforcement intended to bear heavy loads and to be inflated to relatively high pressures, and particularly to tires suited for use as airplane tires.
The radial carcass reinforcements of such tires generally have several plies of textile cables which are anchored in each bead to at least one bead wire and generally to a single bead wire. The reinforcement elements of these tires are wound around said bead wire from the inside to the outside, forming upturns the ends of which are spaced radially from the axis of rotation of the tire. The severe conditions under which airplane tires are used, and, in particular, the overloads imposed, are such that the fatigue strength endurance of the beads is slight, particularly at the place of the ends of the upturns of the carcass reinforcement.
A substantial improvement in performance is obtained by separating the plies of the carcass reinforcement into two groups. The first group comprises the axially inner carcass reinforcement plies in the region of the beads, these plies being then wound around a bead wire in each bead from the inside to the outside of the tire. The second group is formed of at least one axially outer ply in the region of the beads, which ply is generally wound around the bead wire going from the outside to the inside of the tire.
Such arrangements are known and are shown, for instance, in U.S. Pat. No. 4,244,414 (FIG. 2).
The fatigue strength of the beads formed in this manner is, however, still insufficient and this lack of fatigue strength results in separations between the outer plies and/or the last outer ply and the rubber which covers it, this rubber forming the outside of the bead and/or of the side wall; these separations are generally accompanied by fatigue of the cables of these plies.